1. Field of the Invention
The present invention relates to an image reading apparatus and an image formation apparatus.
Priority is claimed on Japanese Patent Application No. 2009-296871, filed Dec. 28, 2009 and Japanese Patent Application No. 2009-297258, filed Dec. 28, 2009, the contents of which are incorporated herein by reference.
2. Description of Related Art
An image formation apparatus has, for example, an image reading apparatus that is provided with a light source apparatus which is used to illuminate an original document. There is a light source apparatus with a light source that emits light, and with a light guide (i.e., a light guide device) that guides light emitted from this light source onto an irradiation area. According to this type of image reading apparatus, light emitted from the light source is guided by the light guide and is focused on the irradiation area, and the illuminance of the light in the irradiation area can be increased.
In an image reading apparatus in which the above described light source apparatus is mounted, image data is obtained by using light-receiving sensors such as CCD (charge-coupled devices) and the like to receive feedback light from the original document that is generated as a result of the light from the light source apparatus being irradiated onto the original document. It is assumed that the light that is received by this type of light-receiving sensor is light that has been scattered on the original document. Because of this, when strong light such as light that has been directly reflected from the original document is irradiated onto the light-receiving sensor, image data that differs from the image which is formed on the original document ends up being created, and this prevents superior image data being acquired.
In order to solve this type of problem, an image reading apparatus having a light source apparatus in which a diffusion plate (i.e., a diffusion component) is fitted in the light guide so that strong light that would prevent superior image data being acquired is not contained in the feedback light from the original document is proposed. More specifically, a diffusion plate is fitted at a light emission end surface in a light guide and light emitted from this emission end surface is diffused. As a result, the illuminance distribution of the light that is irradiated onto the original document is uniformized so that the inclusion of strong light intruding into the feedback light is suppressed.
However, in instances such as, for example, when light is irradiated from a plurality of directions onto an original document, there are cases when a plurality of light emission end surfaces is provided in the light guide. In cases such as this, it is preferable for diffusion plates to be provided at all of the emission end surfaces. However, in a conventional image reading apparatus, when a light guide has a plurality of emission end surfaces, the light guide has portions that protrude onto the light emission direction side from the edges of either the emission end surfaces. Because of this, the provision of a diffusion plate over the entire emission end surface in order to avoid any interference between the protruding portions and the diffusion plate has not been possible. In cases such as this in which it is not possible to provide a diffusion plate over an entire emission end surface, a portion of the light emitted from this emission end surface either reaches the original document (i.e., the irradiation area) without passing through the diffusion plate or becomes leakage light. If a portion of the light emitted from an emission end surface reaches the original document (i.e., the irradiation area) without passing through the diffusion plate, then it is not possible to sufficiently uniformize the illuminance distribution of the light irradiated onto the original document (i.e., the irradiation area). Furthermore, if a portion of the light emitted from an emission end surface becomes leakage light, then the efficiency with which the light is utilized is reduced.
Moreover, it is desirable for the illuminance of light in an irradiation area to be high, particularly in an image reading apparatuses installed in an image formation apparatus or the like. In recent years, the use of LED (light emitting diodes) as light sources has been proposed, however, devices that enable a greater quantity of light to be focused onto the irradiation area are being demanded. In addition, in an image reading apparatus provided with light sources and a light guide, in order to more easily increase the light illuminance in an irradiated area, a structure is employed in which a greater quantity of light is acquired inside the light guide by causing the light sources and the light guide to come into mutual contact with each other.
However, because a normal light source generates heat by emitting light, if the light sources are brought into contact with the light guide, the light guide is deformed by the heat from the light sources and there is a possibility that this will interfere with the guiding of light emitted from the light source. In addition, if an LED is brought into contact with a light guide, there is a possibility that the LED will be broken as a result of errors in installation and the like.